/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)queue.h	8.5 (Berkeley) 8/20/94
 * $FreeBSD$
 */

#ifndef _SYS_QUEUE_H_
#define _SYS_QUEUE_H_

#ifdef __cplusplus
extern "C" {
#endif

#include "../ext4_config.h"

/*
 * This file defines four types of data structures: singly-linked lists,
 * singly-linked tail queues, lists and tail queues.
 *
 * A singly-linked list is headed by a single forward pointer. The elements
 * are singly linked for minimum space and pointer manipulation overhead at
 * the expense of O(n) removal for arbitrary elements. New elements can be
 * added to the list after an existing element or at the head of the list.
 * Elements being removed from the head of the list should use the explicit
 * macro for this purpose for optimum efficiency. A singly-linked list may
 * only be traversed in the forward direction.  Singly-linked lists are ideal
 * for applications with large datasets and few or no removals or for
 * implementing a LIFO queue.
 *
 * A singly-linked tail queue is headed by a pair of pointers, one to the
 * head of the list and the other to the tail of the list. The elements are
 * singly linked for minimum space and pointer manipulation overhead at the
 * expense of O(n) removal for arbitrary elements. New elements can be added
 * to the list after an existing element, at the head of the list, or at the
 * end of the list. Elements being removed from the head of the tail queue
 * should use the explicit macro for this purpose for optimum efficiency.
 * A singly-linked tail queue may only be traversed in the forward direction.
 * Singly-linked tail queues are ideal for applications with large datasets
 * and few or no removals or for implementing a FIFO queue.
 *
 * A list is headed by a single forward pointer (or an array of forward
 * pointers for a hash table header). The elements are doubly linked
 * so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before
 * or after an existing element or at the head of the list. A list
 * may be traversed in either direction.
 *
 * A tail queue is headed by a pair of pointers, one to the head of the
 * list and the other to the tail of the list. The elements are doubly
 * linked so that an arbitrary element can be removed without a need to
 * traverse the list. New elements can be added to the list before or
 * after an existing element, at the head of the list, or at the end of
 * the list. A tail queue may be traversed in either direction.
 *
 * For details on the use of these macros, see the queue(3) manual page.
 *
 *
 *				SLIST	LIST	STAILQ	TAILQ
 * _HEAD			+	+	+	+
 * _HEAD_INITIALIZER		+	+	+	+
 * _ENTRY			+	+	+	+
 * _INIT			+	+	+	+
 * _EMPTY			+	+	+	+
 * _FIRST			+	+	+	+
 * _NEXT			+	+	+	+
 * _PREV			-	+	-	+
 * _LAST			-	-	+	+
 * _FOREACH			+	+	+	+
 * _FOREACH_FROM		+	+	+	+
 * _FOREACH_SAFE		+	+	+	+
 * _FOREACH_FROM_SAFE		+	+	+	+
 * _FOREACH_REVERSE		-	-	-	+
 * _FOREACH_REVERSE_FROM	-	-	-	+
 * _FOREACH_REVERSE_SAFE	-	-	-	+
 * _FOREACH_REVERSE_FROM_SAFE	-	-	-	+
 * _INSERT_HEAD			+	+	+	+
 * _INSERT_BEFORE		-	+	-	+
 * _INSERT_AFTER		+	+	+	+
 * _INSERT_TAIL			-	-	+	+
 * _CONCAT			-	-	+	+
 * _REMOVE_AFTER		+	-	+	-
 * _REMOVE_HEAD			+	-	+	-
 * _REMOVE			+	+	+	+
 * _SWAP			+	+	+	+
 *
 */
#ifdef QUEUE_MACRO_DEBUG
/* Store the last 2 places the queue element or head was altered */
struct qm_trace {
    unsigned long lastline;
    unsigned long prevline;
    const char *lastfile;
    const char *prevfile;
};

#define TRACEBUF struct qm_trace trace;
#define TRACEBUF_INITIALIZER {__LINE__, 0, __FILE__, NULL},
#define TRASHIT(x)                                                             \
    do {                                                                       \
        (x) = (void *)-1;                                                      \
    } while (0)
#define QMD_SAVELINK(name, link) void **name = (void *)&(link)

#define QMD_TRACE_HEAD(head)                                                   \
    do {                                                                       \
        (head)->trace.prevline = (head)->trace.lastline;                       \
        (head)->trace.prevfile = (head)->trace.lastfile;                       \
        (head)->trace.lastline = __LINE__;                                     \
        (head)->trace.lastfile = __FILE__;                                     \
    } while (0)

#define QMD_TRACE_ELEM(elem)                                                   \
    do {                                                                       \
        (elem)->trace.prevline = (elem)->trace.lastline;                       \
        (elem)->trace.prevfile = (elem)->trace.lastfile;                       \
        (elem)->trace.lastline = __LINE__;                                     \
        (elem)->trace.lastfile = __FILE__;                                     \
    } while (0)

#else
#define QMD_TRACE_ELEM(elem)
#define QMD_TRACE_HEAD(head)
#define QMD_SAVELINK(name, link)
#define TRACEBUF
#define TRACEBUF_INITIALIZER
#define TRASHIT(x)
#endif /* QUEUE_MACRO_DEBUG */

/*
 * Singly-linked List declarations.
 */
#define SLIST_HEAD(name, type)                                                 \
    struct name {                                                              \
        struct type *slh_first; /* first element */                            \
    }

#define SLIST_HEAD_INITIALIZER(head) {NULL}

#define SLIST_ENTRY(type)                                                      \
    struct {                                                                   \
        struct type *sle_next; /* next element */                              \
    }

/*
 * Singly-linked List functions.
 */
#define SLIST_EMPTY(head) ((head)->slh_first == NULL)

#define SLIST_FIRST(head) ((head)->slh_first)

#define SLIST_FOREACH(var, head, field)                                        \
    for ((var) = SLIST_FIRST((head)); (var); (var) = SLIST_NEXT((var), field))

#define SLIST_FOREACH_FROM(var, head, field)                                   \
    for ((var) = ((var) ? (var) : SLIST_FIRST((head))); (var);                 \
         (var) = SLIST_NEXT((var), field))

#define SLIST_FOREACH_SAFE(var, head, field, tvar)                             \
    for ((var) = SLIST_FIRST((head));                                          \
         (var) && ((tvar) = SLIST_NEXT((var), field), 1); (var) = (tvar))

#define SLIST_FOREACH_FROM_SAFE(var, head, field, tvar)                        \
    for ((var) = ((var) ? (var) : SLIST_FIRST((head)));                        \
         (var) && ((tvar) = SLIST_NEXT((var), field), 1); (var) = (tvar))

#define SLIST_FOREACH_PREVPTR(var, varp, head, field)                          \
    for ((varp) = &SLIST_FIRST((head)); ((var) = *(varp)) != NULL;             \
         (varp) = &SLIST_NEXT((var), field))

#define SLIST_INIT(head)                                                       \
    do {                                                                       \
        SLIST_FIRST((head)) = NULL;                                            \
    } while (0)

#define SLIST_INSERT_AFTER(slistelm, elm, field)                               \
    do {                                                                       \
        SLIST_NEXT((elm), field) = SLIST_NEXT((slistelm), field);              \
        SLIST_NEXT((slistelm), field) = (elm);                                 \
    } while (0)

#define SLIST_INSERT_HEAD(head, elm, field)                                    \
    do {                                                                       \
        SLIST_NEXT((elm), field) = SLIST_FIRST((head));                        \
        SLIST_FIRST((head)) = (elm);                                           \
    } while (0)

#define SLIST_NEXT(elm, field) ((elm)->field.sle_next)

#define SLIST_REMOVE(head, elm, type, field)                                   \
    do {                                                                       \
        QMD_SAVELINK(oldnext, (elm)->field.sle_next);                          \
        if (SLIST_FIRST((head)) == (elm)) {                                    \
            SLIST_REMOVE_HEAD((head), field);                                  \
        } else {                                                               \
            struct type *curelm = SLIST_FIRST((head));                         \
            while (SLIST_NEXT(curelm, field) != (elm))                         \
                curelm = SLIST_NEXT(curelm, field);                            \
            SLIST_REMOVE_AFTER(curelm, field);                                 \
        }                                                                      \
        TRASHIT(*oldnext);                                                     \
    } while (0)

#define SLIST_REMOVE_AFTER(elm, field)                                         \
    do {                                                                       \
        SLIST_NEXT(elm, field) = SLIST_NEXT(SLIST_NEXT(elm, field), field);    \
    } while (0)

#define SLIST_REMOVE_HEAD(head, field)                                         \
    do {                                                                       \
        SLIST_FIRST((head)) = SLIST_NEXT(SLIST_FIRST((head)), field);          \
    } while (0)

#define SLIST_SWAP(head1, head2, type)                                         \
    do {                                                                       \
        struct type *swap_first = SLIST_FIRST(head1);                          \
        SLIST_FIRST(head1) = SLIST_FIRST(head2);                               \
        SLIST_FIRST(head2) = swap_first;                                       \
    } while (0)

/*
 * Singly-linked Tail queue declarations.
 */
#define STAILQ_HEAD(name, type)                                                \
    struct name {                                                              \
        struct type *stqh_first; /* first element */                           \
        struct type **stqh_last; /* addr of last next element */               \
    }

#define STAILQ_HEAD_INITIALIZER(head) {NULL, &(head).stqh_first}

#define STAILQ_ENTRY(type)                                                     \
    struct {                                                                   \
        struct type *stqe_next; /* next element */                             \
    }

/*
 * Singly-linked Tail queue functions.
 */
#define STAILQ_CONCAT(head1, head2)                                            \
    do {                                                                       \
        if (!STAILQ_EMPTY((head2))) {                                          \
            *(head1)->stqh_last = (head2)->stqh_first;                         \
            (head1)->stqh_last = (head2)->stqh_last;                           \
            STAILQ_INIT((head2));                                              \
        }                                                                      \
    } while (0)

#define STAILQ_EMPTY(head) ((head)->stqh_first == NULL)

#define STAILQ_FIRST(head) ((head)->stqh_first)

#define STAILQ_FOREACH(var, head, field)                                       \
    for ((var) = STAILQ_FIRST((head)); (var); (var) = STAILQ_NEXT((var), field))

#define STAILQ_FOREACH_FROM(var, head, field)                                  \
    for ((var) = ((var) ? (var) : STAILQ_FIRST((head))); (var);                \
         (var) = STAILQ_NEXT((var), field))

#define STAILQ_FOREACH_SAFE(var, head, field, tvar)                            \
    for ((var) = STAILQ_FIRST((head));                                         \
         (var) && ((tvar) = STAILQ_NEXT((var), field), 1); (var) = (tvar))

#define STAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                       \
    for ((var) = ((var) ? (var) : STAILQ_FIRST((head)));                       \
         (var) && ((tvar) = STAILQ_NEXT((var), field), 1); (var) = (tvar))

#define STAILQ_INIT(head)                                                      \
    do {                                                                       \
        STAILQ_FIRST((head)) = NULL;                                           \
        (head)->stqh_last = &STAILQ_FIRST((head));                             \
    } while (0)

#define STAILQ_INSERT_AFTER(head, tqelm, elm, field)                           \
    do {                                                                       \
        if ((STAILQ_NEXT((elm), field) = STAILQ_NEXT((tqelm), field)) == NULL) \
            (head)->stqh_last = &STAILQ_NEXT((elm), field);                    \
        STAILQ_NEXT((tqelm), field) = (elm);                                   \
    } while (0)

#define STAILQ_INSERT_HEAD(head, elm, field)                                   \
    do {                                                                       \
        if ((STAILQ_NEXT((elm), field) = STAILQ_FIRST((head))) == NULL)        \
            (head)->stqh_last = &STAILQ_NEXT((elm), field);                    \
        STAILQ_FIRST((head)) = (elm);                                          \
    } while (0)

#define STAILQ_INSERT_TAIL(head, elm, field)                                   \
    do {                                                                       \
        STAILQ_NEXT((elm), field) = NULL;                                      \
        *(head)->stqh_last = (elm);                                            \
        (head)->stqh_last = &STAILQ_NEXT((elm), field);                        \
    } while (0)

#define STAILQ_LAST(head, type, field)                                         \
    (STAILQ_EMPTY((head))                                                      \
         ? NULL                                                                \
         : __containerof((head)->stqh_last, struct type, field.stqe_next))

#define STAILQ_NEXT(elm, field) ((elm)->field.stqe_next)

#define STAILQ_REMOVE(head, elm, type, field)                                  \
    do {                                                                       \
        QMD_SAVELINK(oldnext, (elm)->field.stqe_next);                         \
        if (STAILQ_FIRST((head)) == (elm)) {                                   \
            STAILQ_REMOVE_HEAD((head), field);                                 \
        } else {                                                               \
            struct type *curelm = STAILQ_FIRST((head));                        \
            while (STAILQ_NEXT(curelm, field) != (elm))                        \
                curelm = STAILQ_NEXT(curelm, field);                           \
            STAILQ_REMOVE_AFTER(head, curelm, field);                          \
        }                                                                      \
        TRASHIT(*oldnext);                                                     \
    } while (0)

#define STAILQ_REMOVE_AFTER(head, elm, field)                                  \
    do {                                                                       \
        if ((STAILQ_NEXT(elm, field) =                                         \
                 STAILQ_NEXT(STAILQ_NEXT(elm, field), field)) == NULL)         \
            (head)->stqh_last = &STAILQ_NEXT((elm), field);                    \
    } while (0)

#define STAILQ_REMOVE_HEAD(head, field)                                        \
    do {                                                                       \
        if ((STAILQ_FIRST((head)) =                                            \
                 STAILQ_NEXT(STAILQ_FIRST((head)), field)) == NULL)            \
            (head)->stqh_last = &STAILQ_FIRST((head));                         \
    } while (0)

#define STAILQ_SWAP(head1, head2, type)                                        \
    do {                                                                       \
        struct type *swap_first = STAILQ_FIRST(head1);                         \
        struct type **swap_last = (head1)->stqh_last;                          \
        STAILQ_FIRST(head1) = STAILQ_FIRST(head2);                             \
        (head1)->stqh_last = (head2)->stqh_last;                               \
        STAILQ_FIRST(head2) = swap_first;                                      \
        (head2)->stqh_last = swap_last;                                        \
        if (STAILQ_EMPTY(head1))                                               \
            (head1)->stqh_last = &STAILQ_FIRST(head1);                         \
        if (STAILQ_EMPTY(head2))                                               \
            (head2)->stqh_last = &STAILQ_FIRST(head2);                         \
    } while (0)

/*
 * List declarations.
 */
#define LIST_HEAD(name, type)                                                  \
    struct name {                                                              \
        struct type *lh_first; /* first element */                             \
    }

#define LIST_HEAD_INITIALIZER(head) {NULL}

#define LIST_ENTRY(type)                                                       \
    struct {                                                                   \
        struct type *le_next;  /* next element */                              \
        struct type **le_prev; /* address of previous next element */          \
    }

/*
 * List functions.
 */

#if (defined(_KERNEL) && defined(INVARIANTS))
#define QMD_LIST_CHECK_HEAD(head, field)                                       \
    do {                                                                       \
        if (LIST_FIRST((head)) != NULL &&                                      \
            LIST_FIRST((head))->field.le_prev != &LIST_FIRST((head)))          \
            panic("Bad list head %p first->prev != head", (head));             \
    } while (0)

#define QMD_LIST_CHECK_NEXT(elm, field)                                        \
    do {                                                                       \
        if (LIST_NEXT((elm), field) != NULL &&                                 \
            LIST_NEXT((elm), field)->field.le_prev != &((elm)->field.le_next)) \
            panic("Bad link elm %p next->prev != elm", (elm));                 \
    } while (0)

#define QMD_LIST_CHECK_PREV(elm, field)                                        \
    do {                                                                       \
        if (*(elm)->field.le_prev != (elm))                                    \
            panic("Bad link elm %p prev->next != elm", (elm));                 \
    } while (0)
#else
#define QMD_LIST_CHECK_HEAD(head, field)
#define QMD_LIST_CHECK_NEXT(elm, field)
#define QMD_LIST_CHECK_PREV(elm, field)
#endif /* (_KERNEL && INVARIANTS) */

#define LIST_EMPTY(head) ((head)->lh_first == NULL)

#define LIST_FIRST(head) ((head)->lh_first)

#define LIST_FOREACH(var, head, field)                                         \
    for ((var) = LIST_FIRST((head)); (var); (var) = LIST_NEXT((var), field))

#define LIST_FOREACH_FROM(var, head, field)                                    \
    for ((var) = ((var) ? (var) : LIST_FIRST((head))); (var);                  \
         (var) = LIST_NEXT((var), field))

#define LIST_FOREACH_SAFE(var, head, field, tvar)                              \
    for ((var) = LIST_FIRST((head));                                           \
         (var) && ((tvar) = LIST_NEXT((var), field), 1); (var) = (tvar))

#define LIST_FOREACH_FROM_SAFE(var, head, field, tvar)                         \
    for ((var) = ((var) ? (var) : LIST_FIRST((head)));                         \
         (var) && ((tvar) = LIST_NEXT((var), field), 1); (var) = (tvar))

#define LIST_INIT(head)                                                        \
    do {                                                                       \
        LIST_FIRST((head)) = NULL;                                             \
    } while (0)

#define LIST_INSERT_AFTER(listelm, elm, field)                                 \
    do {                                                                       \
        QMD_LIST_CHECK_NEXT(listelm, field);                                   \
        if ((LIST_NEXT((elm), field) = LIST_NEXT((listelm), field)) != NULL)   \
            LIST_NEXT((listelm), field)->field.le_prev =                       \
                &LIST_NEXT((elm), field);                                      \
        LIST_NEXT((listelm), field) = (elm);                                   \
        (elm)->field.le_prev = &LIST_NEXT((listelm), field);                   \
    } while (0)

#define LIST_INSERT_BEFORE(listelm, elm, field)                                \
    do {                                                                       \
        QMD_LIST_CHECK_PREV(listelm, field);                                   \
        (elm)->field.le_prev = (listelm)->field.le_prev;                       \
        LIST_NEXT((elm), field) = (listelm);                                   \
        *(listelm)->field.le_prev = (elm);                                     \
        (listelm)->field.le_prev = &LIST_NEXT((elm), field);                   \
    } while (0)

#define LIST_INSERT_HEAD(head, elm, field)                                     \
    do {                                                                       \
        QMD_LIST_CHECK_HEAD((head), field);                                    \
        if ((LIST_NEXT((elm), field) = LIST_FIRST((head))) != NULL)            \
            LIST_FIRST((head))->field.le_prev = &LIST_NEXT((elm), field);      \
        LIST_FIRST((head)) = (elm);                                            \
        (elm)->field.le_prev = &LIST_FIRST((head));                            \
    } while (0)

#define LIST_NEXT(elm, field) ((elm)->field.le_next)

#define LIST_PREV(elm, head, type, field)                                      \
    ((elm)->field.le_prev == &LIST_FIRST((head))                               \
         ? NULL                                                                \
         : __containerof((elm)->field.le_prev, struct type, field.le_next))

#define LIST_REMOVE(elm, field)                                                \
    do {                                                                       \
        QMD_SAVELINK(oldnext, (elm)->field.le_next);                           \
        QMD_SAVELINK(oldprev, (elm)->field.le_prev);                           \
        QMD_LIST_CHECK_NEXT(elm, field);                                       \
        QMD_LIST_CHECK_PREV(elm, field);                                       \
        if (LIST_NEXT((elm), field) != NULL)                                   \
            LIST_NEXT((elm), field)->field.le_prev = (elm)->field.le_prev;     \
        *(elm)->field.le_prev = LIST_NEXT((elm), field);                       \
        TRASHIT(*oldnext);                                                     \
        TRASHIT(*oldprev);                                                     \
    } while (0)

#define LIST_SWAP(head1, head2, type, field)                                   \
    do {                                                                       \
        struct type *swap_tmp = LIST_FIRST((head1));                           \
        LIST_FIRST((head1)) = LIST_FIRST((head2));                             \
        LIST_FIRST((head2)) = swap_tmp;                                        \
        if ((swap_tmp = LIST_FIRST((head1))) != NULL)                          \
            swap_tmp->field.le_prev = &LIST_FIRST((head1));                    \
        if ((swap_tmp = LIST_FIRST((head2))) != NULL)                          \
            swap_tmp->field.le_prev = &LIST_FIRST((head2));                    \
    } while (0)

/*
 * Tail queue declarations.
 */
#define TAILQ_HEAD(name, type)                                                 \
    struct name {                                                              \
        struct type *tqh_first; /* first element */                            \
        struct type **tqh_last; /* addr of last next element */                \
        TRACEBUF                                                               \
    }

#define TAILQ_HEAD_INITIALIZER(head)                                           \
    {NULL, &(head).tqh_first, TRACEBUF_INITIALIZER}

#define TAILQ_ENTRY(type)                                                      \
    struct {                                                                   \
        struct type *tqe_next;  /* next element */                             \
        struct type **tqe_prev; /* address of previous next element */         \
        TRACEBUF                                                               \
    }

/*
 * Tail queue functions.
 */
#if (defined(_KERNEL) && defined(INVARIANTS))
#define QMD_TAILQ_CHECK_HEAD(head, field)                                      \
    do {                                                                       \
        if (!TAILQ_EMPTY(head) &&                                              \
            TAILQ_FIRST((head))->field.tqe_prev != &TAILQ_FIRST((head)))       \
            panic("Bad tailq head %p first->prev != head", (head));            \
    } while (0)

#define QMD_TAILQ_CHECK_TAIL(head, field)                                      \
    do {                                                                       \
        if (*(head)->tqh_last != NULL)                                         \
            panic("Bad tailq NEXT(%p->tqh_last) != NULL", (head));             \
    } while (0)

#define QMD_TAILQ_CHECK_NEXT(elm, field)                                       \
    do {                                                                       \
        if (TAILQ_NEXT((elm), field) != NULL &&                                \
            TAILQ_NEXT((elm), field)->field.tqe_prev !=                        \
                &((elm)->field.tqe_next))                                      \
            panic("Bad link elm %p next->prev != elm", (elm));                 \
    } while (0)

#define QMD_TAILQ_CHECK_PREV(elm, field)                                       \
    do {                                                                       \
        if (*(elm)->field.tqe_prev != (elm))                                   \
            panic("Bad link elm %p prev->next != elm", (elm));                 \
    } while (0)
#else
#define QMD_TAILQ_CHECK_HEAD(head, field)
#define QMD_TAILQ_CHECK_TAIL(head, headname)
#define QMD_TAILQ_CHECK_NEXT(elm, field)
#define QMD_TAILQ_CHECK_PREV(elm, field)
#endif /* (_KERNEL && INVARIANTS) */

#define TAILQ_CONCAT(head1, head2, field)                                      \
    do {                                                                       \
        if (!TAILQ_EMPTY(head2)) {                                             \
            *(head1)->tqh_last = (head2)->tqh_first;                           \
            (head2)->tqh_first->field.tqe_prev = (head1)->tqh_last;            \
            (head1)->tqh_last = (head2)->tqh_last;                             \
            TAILQ_INIT((head2));                                               \
            QMD_TRACE_HEAD(head1);                                             \
            QMD_TRACE_HEAD(head2);                                             \
        }                                                                      \
    } while (0)

#define TAILQ_EMPTY(head) ((head)->tqh_first == NULL)

#define TAILQ_FIRST(head) ((head)->tqh_first)

#define TAILQ_FOREACH(var, head, field)                                        \
    for ((var) = TAILQ_FIRST((head)); (var); (var) = TAILQ_NEXT((var), field))

#define TAILQ_FOREACH_FROM(var, head, field)                                   \
    for ((var) = ((var) ? (var) : TAILQ_FIRST((head))); (var);                 \
         (var) = TAILQ_NEXT((var), field))

#define TAILQ_FOREACH_SAFE(var, head, field, tvar)                             \
    for ((var) = TAILQ_FIRST((head));                                          \
         (var) && ((tvar) = TAILQ_NEXT((var), field), 1); (var) = (tvar))

#define TAILQ_FOREACH_FROM_SAFE(var, head, field, tvar)                        \
    for ((var) = ((var) ? (var) : TAILQ_FIRST((head)));                        \
         (var) && ((tvar) = TAILQ_NEXT((var), field), 1); (var) = (tvar))

#define TAILQ_FOREACH_REVERSE(var, head, headname, field)                      \
    for ((var) = TAILQ_LAST((head), headname); (var);                          \
         (var) = TAILQ_PREV((var), headname, field))

#define TAILQ_FOREACH_REVERSE_FROM(var, head, headname, field)                 \
    for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname)); (var);        \
         (var) = TAILQ_PREV((var), headname, field))

#define TAILQ_FOREACH_REVERSE_SAFE(var, head, headname, field, tvar)           \
    for ((var) = TAILQ_LAST((head), headname);                                 \
         (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);            \
         (var) = (tvar))

#define TAILQ_FOREACH_REVERSE_FROM_SAFE(var, head, headname, field, tvar)      \
    for ((var) = ((var) ? (var) : TAILQ_LAST((head), headname));               \
         (var) && ((tvar) = TAILQ_PREV((var), headname, field), 1);            \
         (var) = (tvar))

#define TAILQ_INIT(head)                                                       \
    do {                                                                       \
        TAILQ_FIRST((head)) = NULL;                                            \
        (head)->tqh_last = &TAILQ_FIRST((head));                               \
        QMD_TRACE_HEAD(head);                                                  \
    } while (0)

#define TAILQ_INSERT_AFTER(head, listelm, elm, field)                          \
    do {                                                                       \
        QMD_TAILQ_CHECK_NEXT(listelm, field);                                  \
        if ((TAILQ_NEXT((elm), field) = TAILQ_NEXT((listelm), field)) != NULL) \
            TAILQ_NEXT((elm), field)->field.tqe_prev =                         \
                &TAILQ_NEXT((elm), field);                                     \
        else {                                                                 \
            (head)->tqh_last = &TAILQ_NEXT((elm), field);                      \
            QMD_TRACE_HEAD(head);                                              \
        }                                                                      \
        TAILQ_NEXT((listelm), field) = (elm);                                  \
        (elm)->field.tqe_prev = &TAILQ_NEXT((listelm), field);                 \
        QMD_TRACE_ELEM(&(elm)->field);                                         \
        QMD_TRACE_ELEM(&(listelm)->field);                                     \
    } while (0)

#define TAILQ_INSERT_BEFORE(listelm, elm, field)                               \
    do {                                                                       \
        QMD_TAILQ_CHECK_PREV(listelm, field);                                  \
        (elm)->field.tqe_prev = (listelm)->field.tqe_prev;                     \
        TAILQ_NEXT((elm), field) = (listelm);                                  \
        *(listelm)->field.tqe_prev = (elm);                                    \
        (listelm)->field.tqe_prev = &TAILQ_NEXT((elm), field);                 \
        QMD_TRACE_ELEM(&(elm)->field);                                         \
        QMD_TRACE_ELEM(&(listelm)->field);                                     \
    } while (0)

#define TAILQ_INSERT_HEAD(head, elm, field)                                    \
    do {                                                                       \
        QMD_TAILQ_CHECK_HEAD(head, field);                                     \
        if ((TAILQ_NEXT((elm), field) = TAILQ_FIRST((head))) != NULL)          \
            TAILQ_FIRST((head))->field.tqe_prev = &TAILQ_NEXT((elm), field);   \
        else                                                                   \
            (head)->tqh_last = &TAILQ_NEXT((elm), field);                      \
        TAILQ_FIRST((head)) = (elm);                                           \
        (elm)->field.tqe_prev = &TAILQ_FIRST((head));                          \
        QMD_TRACE_HEAD(head);                                                  \
        QMD_TRACE_ELEM(&(elm)->field);                                         \
    } while (0)

#define TAILQ_INSERT_TAIL(head, elm, field)                                    \
    do {                                                                       \
        QMD_TAILQ_CHECK_TAIL(head, field);                                     \
        TAILQ_NEXT((elm), field) = NULL;                                       \
        (elm)->field.tqe_prev = (head)->tqh_last;                              \
        *(head)->tqh_last = (elm);                                             \
        (head)->tqh_last = &TAILQ_NEXT((elm), field);                          \
        QMD_TRACE_HEAD(head);                                                  \
        QMD_TRACE_ELEM(&(elm)->field);                                         \
    } while (0)

#define TAILQ_LAST(head, headname)                                             \
    (*(((struct headname *)((head)->tqh_last))->tqh_last))

#define TAILQ_NEXT(elm, field) ((elm)->field.tqe_next)

#define TAILQ_PREV(elm, headname, field)                                       \
    (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))

#define TAILQ_REMOVE(head, elm, field)                                         \
    do {                                                                       \
        QMD_SAVELINK(oldnext, (elm)->field.tqe_next);                          \
        QMD_SAVELINK(oldprev, (elm)->field.tqe_prev);                          \
        QMD_TAILQ_CHECK_NEXT(elm, field);                                      \
        QMD_TAILQ_CHECK_PREV(elm, field);                                      \
        if ((TAILQ_NEXT((elm), field)) != NULL)                                \
            TAILQ_NEXT((elm), field)->field.tqe_prev = (elm)->field.tqe_prev;  \
        else {                                                                 \
            (head)->tqh_last = (elm)->field.tqe_prev;                          \
            QMD_TRACE_HEAD(head);                                              \
        }                                                                      \
        *(elm)->field.tqe_prev = TAILQ_NEXT((elm), field);                     \
        TRASHIT(*oldnext);                                                     \
        TRASHIT(*oldprev);                                                     \
        QMD_TRACE_ELEM(&(elm)->field);                                         \
    } while (0)

#define TAILQ_SWAP(head1, head2, type, field)                                  \
    do {                                                                       \
        struct type *swap_first = (head1)->tqh_first;                          \
        struct type **swap_last = (head1)->tqh_last;                           \
        (head1)->tqh_first = (head2)->tqh_first;                               \
        (head1)->tqh_last = (head2)->tqh_last;                                 \
        (head2)->tqh_first = swap_first;                                       \
        (head2)->tqh_last = swap_last;                                         \
        if ((swap_first = (head1)->tqh_first) != NULL)                         \
            swap_first->field.tqe_prev = &(head1)->tqh_first;                  \
        else                                                                   \
            (head1)->tqh_last = &(head1)->tqh_first;                           \
        if ((swap_first = (head2)->tqh_first) != NULL)                         \
            swap_first->field.tqe_prev = &(head2)->tqh_first;                  \
        else                                                                   \
            (head2)->tqh_last = &(head2)->tqh_first;                           \
    } while (0)

#ifdef __cplusplus
}
#endif

#endif /* !_SYS_QUEUE_H_ */
